.DS_StoreはDesktop Service Store
2006年の記事だけども
However, we soon started realizing that the Finder backend would be useful outside of the Finder. Therefore, a plan was hatched to someday make it available as a public API. Since I had previously been responsible for naming Icon Services and Navigation Services, we decided to go with Desktop Services (at the time, we were also considering renaming the Finder to "Desktop"). Hence the name of the .DS_Store, for "Desktop Services Store".
Finderのバックエンドを公開APIとして利用可能にする計画の中で,Desktop Serviceと名付けたのがこの名前の由来らしい.